In the manufacture of semiconductor devices and other ion related products, ion implantation systems are used to impart dopant elements into semiconductor wafers, display panels, or other types of workpieces. Typical ion implantation systems or ion implanters impact a workpiece with an ion beam utilizing a known recipe or process in order to produce n-type or p-type doped regions, or to form passivation layers in the workpiece. When used for doping semiconductors, the ion implantation system injects selected ion species to produce the desired extrinsic material. Typically, dopant atoms or molecules are ionized and isolated, sometimes accelerated or decelerated, formed into a beam, and implanted into a workpiece. The dopant ions physically bombard and enter the surface of the workpiece, and subsequently come to rest below the workpiece surface in the crystalline lattice structure thereof.
Referring initially to FIG. 1, illustrated is a prior art ion implantation system 100 that utilizes an extraction electrode system 200 similar to that of prior art FIG. 2. FIG. 1 illustrates a typical ion implantation system 100 that is operable to scan a workpiece 190 (e.g., a semiconductor substrate or wafer) relative to an ion beam, therein implanting ions into the workpiece 190. FIG. 2 represents a schematic of a prior art extraction electrode system 200 that utilizes a triode type extraction electrode system 200 for extracting an ion beam 30 from an ion source 20 for implantation.
The prior art system 100 (FIG. 1) includes modular gas boxes 164 and 166, and a gas box remote purge control panel 168. The gas boxes 164 and 166 comprise, among other things, one or more gases of a dopant substance, and the boxes 164, 166 facilitate selective delivery of the gas(es) into an ion source 182 within the system 100, wherein the gas(es) can be ionized to generate ions suitable for implantation into a wafer or workpiece 190 selectively brought into the system 100. The gas box remote control panel 168 facilitates venting or purging gas(es) or other substances out of the system 100 on an “as needed” or desired basis.
High voltage terminal power distribution 172 and a high voltage isolation transformer 174 are included to, among other things, electrically excite and impart energy to the dopant gas(es) to generate ions. An ion beam extraction assembly 176 is included to extract ions from the ion source 182 and accelerate them into a beamline region 178 illustrated by the bracket in FIG. 1, which includes a mass analysis magnet 180. The mass analysis magnet 180 is operable to sort out or reject ions of an inappropriate charge-to-mass ratio. In particular, the mass analysis magnet 180 comprises a guide having curved sidewalls into which ions of an undesired mass-to-charge ratio collide as they are propagated through the beamguide by way of one or more magnetic fields generated by magnet(s) of the mass analysis magnet 180.
A component 184 may be included to assist with controlling the angle of the scanned ion beam. This may include, among other things, a scan angle correction lens. An acceleration/deceleration column 186 facilitates controlling and adjusting the speed, and/or focusing, of ions within the ion beam. A component 188 operable to filter out contaminant particles, such as a final energy filter is also included to mitigate energy contaminating particles from encountering the workpiece 190.
Wafers and/or workpieces 190 are loaded into an end station chamber 192 for selective implantation with ions. A mechanical scan drive 194 maneuvers the workpieces 190 within the chamber 192 to facilitate selective encounters with the ion beam. The wafers or workpieces 190 are moved into the end station chamber 192 by a workpiece handling system 196, which may include, for example, one or more mechanical or robotic arms 197. An operator console 198 allows an operator to regulate the implantation process by selectively controlling one or more components of the system 100. Finally, a power distribution box 199 is included to provide power to the overall system 100.
Referring again to prior art FIG. 2, the ion source 20 and the extraction electrodes are illustrated schematically as a cross sectional side view which utilize a triode extraction assembly, as disclosed in U.S. Pat. No. 6,501,078. The ion source 20 comprises an arc chamber 20A mounted to a housing 15. A bushing 20B acts as an insulator to isolate the ion source 20 from the remainder of the housing 15. Ions formed in the arc chamber 20A are extracted from the source 20 through an exit aperture 21 in a front face 22 of the source 20. The front face 22 of the ion source 20 forms a first apertured source electrode at the potential of the ion source 20. The extraction electrodes are illustrated in FIG. 2 by suppression and ground apertured electrodes 24, 25 respectively. Each of the apertured electrodes 24, 25 comprise a single electrically conductive plate having an aperture through the plate to allow the ion beam emerging from the ion source 20 to pass through. Each aperture has an elongated slot configuration with the direction of elongation being perpendicular to the plane in FIG. 2. In other words the slot has its long dimension along the z axis, as shown, with the positive z axis going into the paper.
For a beam of positive ions, the ion source 20 is maintained by a voltage supply at a positive voltage relative to ground. The ground electrode 25 restricts the penetration of the electric fields between the ground electrode 25 and the ion source 20 into the region to the right (in FIG. 2) of the ground electrode 25.
The energy of the ion beam 30 emerging from the extraction assembly 200 is determined by the voltage supplied to the ion source 20. A typical value for this voltage is 20 kV, providing extracted beam energy of 20 keV. However, extracted beam energies of 80 keV and higher, or 0.5 keV or lower may also be obtained. To obtain higher or lower beam energies, it is a matter of raising or lowering respectively the source voltage.
The suppression electrode 24 is biased by a voltage supply to a negative potential relative to ground. The negatively biased suppression electrode 24, operates to prevent electrons in the ion beam downstream of the ground electrode 25 (to the right in FIG. 2) from being drawn into the extraction region and into the ion source 20. The suppression and ground electrodes 24, 25 are mounted so as to be movable relatively to the source 20 in the direction of travel of the ion beam 30 as indicated by the arrow x. The apparatus can be “tuned” such that the gap between the extraction and suppression 24 electrodes is larger when the beam energy is larger. The electrodes are further mounted, such that the suppression 24 and ground 25 electrodes are relatively movable laterally in the direction of arrow y, namely in the plane of the paper and approximately perpendicular to the ion beam direction, relative to the source 20. A mechanism is also provided by virtue of which the size of the electrode slit can be adjusted in the lateral direction y as indicated by the y arrows in FIG. 2.
It is an object of the present invention, then to provide an improved variable aperture electrode (VAE) with a variable gap electrode (VGE) that utilizes a pendulum scanning system in a high current ion implantation system. It is a further object to provide an acceleration/deceleration system for use in a high energy ion implantation system that utilizes a pendulum scanning device.